# US 2010/0328138 A1 · Short baseline helicopter positioning radar for low visibility

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- Number: US 2010/0328138 A1
- Document ID: US20100328138A1
- Status: Published application
- Kind: A1
- Application number: 12/768,793
- Filed: 2010-04-28
- Published: 2010-12-30
- Earliest claimed: 2009-05-07
- Assignees: Intelligent Sciences, Ltd.
- Inventors: Jacques Y. GUIGNÉ; James A. STACEY; Nicholas G. PACE
- Web page: https://patentgrep.com/patent/US20100328138A1

## CPC

- G01S 13/878: {Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector (G01S13/874 takes precedence)}
- G01S 13/913: {for landing purposes}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

A method for determining position and orientation of a rotating wing aircraft (e.g. helicopter) with respect to a ground station includes transmitting an electromagnetic signal from the aircraft. The signal includes a plurality of electromagnetic signals, each signal having a different selected frequency. The signal is detected at an array of sensors disposed on the ground surface in a selected pattern. The array includes at least one reference sensor and at least three spaced apart time difference determination sensors. A difference in arrival time of the signals between the reference sensor and each of the time difference determination sensors is determined and a spatial position of the aircraft is determined from the time differences.

## Claims

### Claim 1

A method for determining position of an aircraft with respect to a ground station, comprising:
transmitting a signal from the aircraft, the signal comprising a plurality of electromagnetic signals, each signal having a different selected frequency;
detecting the signals at an array of sensors disposed on the ground surface in a selected pattern, the array including at least one reference sensor and at least three spaced apart time difference determination sensors;
determining a difference in arrival time of the signals between the reference sensor and each of the time difference determination sensors; and
determining a spatial position of the aircraft from the time differences.

### Claim 2 (depends on 1)

The method of claim 1 wherein the time differences are determined by determining a relationship between a frequency of the signal and a phase difference between signals detected by each of the sensors.

### Claim 3 (depends on 1)

The method of claim 1 wherein the time difference determination sensors are disposed on a circle having a selected radius from a position of the reference sensor.

### Claim 4 (depends on 1)

The method of claim 1 wherein more than four difference determination sensors are used, and such sensors are arranged in a regular, irregular or random array geometry.

### Claim 5 (depends on 1)

The method of claim 1 wherein the selected radius is such that the phase difference does not exceed the value 2π when the aircraft is within a predetermined distance from the array.

### Claim 6 (depends on 1)

The method of claim 1 further comprising deploying the array of sensors from the aircraft prior to landing thereof.

### Claim 7 (depends on 1)

The method of claim 1 further comprising measuring an altitude of the aircraft at a plurality of spaced apart positions and a geodetic orientation of the aircraft thereof, and calibrating an altitude determined from the spatial position using the measured altitudes.

### Claim 8

A method for determining position of an aircraft with respect to a ground station, comprising:
transmitting a signal from the ground station, the signal comprising a plurality of electromagnetic signals, each signal having a different selected frequency;
detecting the signals at an array of sensors disposed on the aircraft in a selected pattern, the array including at least one reference sensor and at least three spaced apart time difference determination sensors;
determining a difference in arrival time of the signals between the reference sensor and each of the time difference determination sensors; and
determining a spatial position of the aircraft from the time differences.

### Claim 9 (depends on 8)

The method of claim 8 wherein the time differences are determined by determining a relationship between a frequency of the signal and a phase difference between signals detected by each of the sensors.

### Claim 10 (depends on 8)

The method of claim 8 wherein the time difference determination sensors are disposed on a circle having a selected radius from a position of the reference sensor.

### Claim 11 (depends on 8)

The method of claim 8 wherein the selected radius is such that the phase difference does not exceed the value 2π when the aircraft is within a predetermined distance from the array.

### Claim 12 (depends on 8)

The method of claim 8 further comprising measuring an altitude of the aircraft at a plurality of spaced apart positions and a geodetic direction thereof, and calibrating an altitude determined from the spatial position using the measured altitudes.